Jack Reynor was born on January 23, 1992, in Longmont, Colorado, to an Irish mother and an American father. He moved to the village of Valleymount, County Wicklow, Ireland, when he was two, and was raised there. In early 2010, Reynor was cast in Kirsten Sheridan's Dollhouse (2012) which debuted at Berlinale 2012. In late 2011 he played the title role in Lenny Abrahamson's highly acclaimed What Richard Did (2012). Other notable roles include the films Transformers: Age of Extinction (2014), Glassland (2014), Macbeth (2015), Sing Street (2016), and Midsommar (2019), as well as the series Strange Angel (2018-2019) and The Peripheral (2022).
Reynor holds dual citizenship of the U.S. and Ireland. He resides in Ireland.
